The presence of oil in the environment is of major concern due to its acute toxicity and impact on human health and the environment. Thus, industries are being required to meet-stringent effluent standards. As a result, finding and developing innovative methods to treat oily waters effectively and economically is a necessity. In the present study, the, potential of bentonite organo-clay (modified bentonite) in the powdered and granular forms was evaluated in the removal of oil from five representative synthetic (standard mineral oil, SMO; kutwell45, KUT45; and valcool, VAL) and actual (refinery effluent, RE and produced water, PW) emulsions by a series of batch and column experiments. Bentonite was used in batch experiments to compare its oil removal efficiency with that of organo-clay. Batch kinetic experiments showed that the equilibrium time was in the range of 1 to 3 hours for bentonite, 2 to 3 hours for powdered organo-clay and 2 to 4 hours for organo-clay/anthracite mixture. The sorption of oil to bentonite was described by the Freundlich model for SMO, KUT45, VAL and PW; it followed the BET isotherm for RE. The sorption of oil to powdered organo-clay followed the Freundlich model for SMO, KUT45 and PW; it followed the Langmuir and the BET models for VAL and RE, respectively. Continuous column experiments using organo-clay/anthracite bed and various oil-in-water emulsions showed that oil removal efficiency decreased with increasing flow rate and increased with increasing depth of bed. A study on breakdown mechanisms for organo-clay/anthracite bed showed that the head-loss across the bed can well be predicted using the Carman-Kozeny filtration model for single-phase flow. It was observed that the Carman-Kozeny model may not yield accurate predictions at high flow rates in the case of two-phase flow. The analysis of the breakthrough data for RE showed that the homogeneous surface diffusion model (HSDM) exhibited a trend similar to observed values for the effluent oil concentration profiles in the case of organo-clay/anthracite beds. Based on the results obtained from batch and column experiments, bentonite organo-clay was an effective medium for oil removal from oily waters. (Abstract shortened by UMI.)